$(document).ready(function() {
    //下拉列表
    $(document).foundation();
})

function getScrollTop(){
    var scrollTop=0; 
    if(document.documentElement&&document.documentElement.scrollTop){ 
        scrollTop=document.documentElement.scrollTop; 
    }else if(document.body){ 
        scrollTop=document.body.scrollTop; 
    } 
    return scrollTop; 
} 
document.onscroll = function(){
    var scrolltop = getScrollTop();
    if(scrolltop >= 80){
        $(".header").addClass("hdxiding");
    }else{
        $(".header").removeClass("hdxiding");
    }
}